1. 添加权限

在AndroidManifest.xml文件中添加以下权限：

2. 获取相机对象

在Activity中获取相机对象：

private Camera mCamera;
// ......
@Override
protected void onResume() {
    super.onResume();
    if (mCamera == null) {
        mCamera = Camera.open();
    }
}
@Override
protected void onPause() {
    super.onPause();
    if (mCamera != null) {
        mCamera.release();
        mCamera = null;
    }
}

3. 设置相机参数

在获取相机对象之后，设置相机参数：

private void setCameraParameters(Camera camera) {
    Camera.Parameters parameters = camera.getParameters();
    // 设置拍照像素为最大值
    List pictureSizes = parameters.getSupportedPictureSizes();
    Camera.Size pictureSize = pictureSizes.get(0);
    for (Camera.Size size : pictureSizes) {
        int sizeInPixel = size.width * size.height;
        int pictureSizeInPixel = pictureSize.width * pictureSize.height;
        if (sizeInPixel > pictureSizeInPixel) {
            pictureSize = size;
        }
    }
    parameters.setPictureSize(pictureSize.width, pictureSize.height);
    camera.setParameters(parameters);
}

4. 拍照

在拍照之前，设置预览画面的显示参数：

private void setPreviewDisplay(Camera camera, SurfaceTexture surfaceTexture) {
    try {
        camera.setPreviewTexture(surfaceTexture);
    } catch (IOException e) {
        e.printStackTrace();
    }
}

然后，将预览画面显示到TextureView上：

private TextureView mTextureView;
// ......
@Override
public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
    setPreviewDisplay(mCamera, surface);
    setCameraParameters(mCamera);
    mCamera.startPreview();
}

最后，拍照并保存图片：

private void takePicture(Camera camera) {
    camera.takePicture(null, null, new Camera.PictureCallback() {
        @Override
        public void onPictureTaken(byte[] data, Camera camera) {
            Bitmap bitmap = BitmapFactory.decodeByteArray(data, 0, data.length);
            try {
                String fileName = Environment.getExternalStorageDirectory().getPath() + "/" + System.currentTimeMillis() + ".jpg";
                FileOutputStream out = new FileOutputStream(fileName);
                bitmap.compress(Bitmap.CompressFormat.JPEG, 100, out);
                out.flush();
                out.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
            camera.startPreview();
        }
    });
}

完整代码如下：

public class MainActivity extends AppCompatActivity implements TextureView.SurfaceTextureListener {
    private static final String TAG = "MainActivity";
    private Camera mCamera;
    private TextureView mTextureView;
    // ......
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mTextureView = findViewById(R.id.textureView);
        mTextureView.setSurfaceTextureListener(this);
    }
    @Override
    protected void onResume() {
        super.onResume();
        if (mCamera == null) {
            mCamera = Camera.open();
        }
    }
    @Override
    protected void onPause() {
        super.onPause();
        if (mCamera != null) {
            mCamera.release();